All structures have their own unique "natural" or "resonant" frequency which is the physical vibration point at which a structure will exhibit violent, even self-destructive vibrations. Those destructive vibrations occur as energy at a specific frequency is applied to an object. A common household example is the washing machine. When a washing machine enters its spin cycle, the wash load must be relatively evenly balanced about the drum. Otherwise, as the drum spins faster and faster, a strong vibrational force will be produced. As this vibration nears the unique natural frequency of the washing machine, the machine will shake violently. If the vibration remains at this frequency, the machine will likely shake itself apart.
Another historical example of destructive resonant vibration on a larger scale is the Tacoma Narrows Bridge disaster in Tacoma, Wash. The bridge was designed as a suspended plate girder bridge and as a result caught wind passing through the span. As the wind intensity increased on Nov. 7, 1940, to 42 m.p.h., a continuous oscillation or rocking motion was created throughout the span of the bridge that grew in intensity until the bridge finally tore apart. Like a washer and the Tacoma Bridge, organs and tissues in the human body have natural resonant frequencies at which they will resonate, resulting in tissue specific destruction.
Various medical devices have been created for removing body tissues and in particular, fat. The differences between these devices essentially depends upon the physical properties of the instrument and the particular tissue to be removed. For example, an ultrasonic device (using high frequency sound waves) can be used to break apart a kidney stone but would have little to no effect on less dense objects such as fat or muscle. A kidney stone is compact and a high frequency ultrasound device can break the stone into smaller pieces for removal. Body fat, on the other hand, is more like a firm gelatin and would simply wiggle if a sound wave was applied.
Some researchers have developed an ultrasonic cannula that vibrates rapidly, destroying neighboring tissue by "melting" the tissues. Unfortunately, nerve, artery and tissue burns result at the ultrasonic frequencies required to break apart fat cells because these frequencies are not specific for fat. This results in scars and other unwanted side effects. Another example of a device used for removing tissue is a laser, which can be used, for example, in cutting atherosclerotic plaques from arteries. This device uses a light wave to incinerate an object, but again, because many tissues absorb laser energy, neighboring nerves and blood vessels are injured concomitantly with fat removal. These medical devices are not useful for removing fat because they employ ultrasonic and laser frequencies not specifically absorbed by fat.
Only when a device employs frequencies of energy at or near the natural frequency of a tissue can complete and safe removal be achieved. Fat, or adipose tissue, is unique in its physical characteristics, requiring a special technique for removal. Being a very distensible tissue, fat easily moves away from any applied force. Presently, the common technique for removing fat and other soft tissues from the body is suctioning tissues into a cannula and subsequent removal with a shearing force. This unfortunately results in excessive damage to lymphatics, nerves and blood vessels, as well as leading to scar formation. Currently, all cannulas used to remove soft tissues such as fat rely on such shearing forces.
As seen in the foregoing discussion, it is preferable for any medical device employed in tissue removal to address the unique "resonant" features of the tissue. As a result, there is a need for a new surgical instrument, designed to remove a variety of tissues, which has the versatility to address the unique resonant properties of the particular tissue, fat in particular, to optimize the removal while decreasing damage to neighboring tissues.